3-Fluoro-2-pyridylmethyl-3-(2,2-difluoro-2-(2-pyridyl)ethylamino)-6-chloro pyrazin-2-one-1-acetamide of formula (I), which is useful as thrombin inhibitor is described in U.S. Pat. No. 6,455,532 B1. The following scheme-A is provided in U.S. Pat. No. 6,455,532 B1 for the preparation of compound of formula (I).

Process for preparing compound of formula (I) is described in WO2002046160 A2 as shown in the following scheme.

Organic Process Research and Development, 2004, 8(2), 192-200 describes a scalable process for the thrombin inhibitor of compound of formula (I). The following synthetic schemes are disclosed.

In order to appropriately develop an efficient, scalable and cost effective process by avoiding expensive and hazardous raw materials in the preparation of compound of formula (I) and its intermediates compared to the above-mentioned processes, we have come out with an improved process as provided in the following.
Described herein is an improved process for the preparation of 3-fluoro-2-pyridyl methyl-3-(2,2-difluoro-2-(2-pyridyl)ethylamino)-6-chloropyrazin-2-one-1-acetamide of compound of formula (I). The improvement comprises the preparation of intermediates namely, 2-aminomethyl-3-fluoropyridine or its salt (K1) and 2,2-difluoro-2-(2-pyridyl)ethylamine or its salt (K2).
The present invention relates to a simple, commercially viable and industrially scalable process for the preparation of compound of the formula (I) and its intermediates, which involves the use of cost effective raw materials, simple isolation of the product, purification and work-up.
The present invention also relates to a simple and industrially scalable process for the preparation of compound of formula (I) and its intermediates, which avoids chromatographic purification techniques.